Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$50.25	12.723%	$56.6433	$56.64	$56.65	$56.60
Purchase #2	$117.75	11.726%	$131.5574	$131.56	$131.55	$131.60
Purchase #3	$222.76	11.551%	$248.491	$248.49	$248.50	$248.50
Purchase #4	$147.90	9.854%	$162.4741	$162.47	$162.45	$162.50
Purchase #5	$197.91	12.265%	$222.1837	$222.18	$222.20	$222.20
Purchase #6	$103.40	8.558%	$112.249	$112.25	$112.25	$112.20
Purchase #7	$233.67	12.687%	$263.3157	$263.32	$263.30	$263.30
7 purchase totals =	$1,073.64		$1,196.9142	$1,196.91	$1,196.90	$1,196.90